New-to-the-trade dozer operators may not be able to fully appreciate the level of operating efficiency and comfort experienced when stepping into the cab of today's modern machines. But more seasoned veterans know full well when someone references the "good old days," they aren't reminiscing about the comfort associated with operating dozers from years past.
"I operated my first bulldozer 40 years ago," says Ed Warner, product manager for dozers, Komatsu. "They used to take a lot of effort, and the seats often felt like you were sitting on nothing more than a crate. Now, being in a dozer is more like being in an SUV, with suspension and air ride seats, armrests and AM/FM radio/cassette players. They're very comfortable and easy to operate."
Shane Thompson, owner of Thompson Grading, Inc., is also more than happy to leave those old models behind. He owns seven dozers — five Komatsu and two Cat units — that he uses in his residential and commercial grading business near Woodruff, SC. Even the progression from machines he purchased as recently as 1999 is significant. "They've gotten a whole lot quicker and a lot less fatiguing on the operators," he says.
Moving toward hydrostatics
Some of the changes to dozers have been relatively minor, such as moving the seat position. However, Thompson believes even this small change is a benefit, since many jobs require operators to turn around and monitor what's happening behind the machine.
Other changes have been more significant, such as the transition to hydrostatic drive. This feature is what Thompson appreciates most about the newer models. "It allows the machine to turn in a lot tighter radius," he says. "And steering is a lot faster."
Hydrostatic drives are becoming increasingly common on many new dozers. According to Brett Errthum, product marketing manager at John Deere, the advantages are twofold: ease of operation and efficiency. "Hydrostatic transmissions are easy to operate because the operator can doze at wide-open throttle at any track speed," he explains. "This enables new operators to gradually increase their speed as their skills improve. The hydrostatics automatically adjust to eliminate the need for the operator to choose the optimum gear for the job at hand. On slopes, the dynamic braking of the hydrostatics allows for predictable control at all times."
The hydrostatic powertrain also achieves maximum efficiency at working speeds when loaded. "At those same low speeds, a torque converter generates heat," Errthum relates. "This heat is a byproduct of lost power. Deere's Total Machine Control (TMC) constantly monitors engine performance and alters pump ratios to maintain peak engine power and efficiency. Performance testing a variety of applications shows the fuel consumption savings compared to a torque converter machine can be as much as 20%, without any compromise in productivity."
New Holland Construction also utilizes a hydrostatic drive system in its DC75, DC85 and DC95 machines. "The answer to which system is more productive — mechanical or hydrostatic — can be debated," says Jorge DeHoyos, brand marketing manager, New Holland Construction. "However, the question of efficiency is not." He notes that hydrostatic components can be sized for the proper track and blade force. "By using over-sized hydrostatic components, our small dozers can out-push and out-pull their respective competitive models."
Ergonomic directional controls
Directional controls have also been updated in many new models.
"In the past, mechanical linkage controls required a good deal of arm strength, and you had to move the controls a great distance," says Warner. "With advanced hydraulics, all that is needed is a very light touch with very short movements."
Many within the industry — manufacturers and contractors alike — compare modern dozer controls to joysticks used for video games. "All that is needed is a very slight movement to control the machine," Warner points out.